Business Segments (Tables)

12 Months Ended

Dec. 31, 2019

Segment Reporting [Abstract]

Summary of Information by Business Segment

Segment Information				Corporate and
(Millions of dollars)	Marketing			Other Assets		Consolidated
Year ended December 31, 2019
Segment income (loss)	$	215.0		(60.2	)	$	154.8
Revenues from external customers	14,034.3			0.3		14,034.6
Interest income	—			3.2		3.2
Interest expense	(0.1		)	(54.8	)	(54.9		)
Loss on early debt extinguishment	—			(14.8	)	(14.8		)
Income tax expense (benefit)	66.3			(18.7	)	47.6
Significant noncash charges (credits)
Depreciation and amortization	138.9			13.3		152.2
Accretion of asset retirement obligations	2.1			—		2.1
Debt extinguishment costs	—			4.4		4.4
Deferred and noncurrent income taxes (benefits)	32.9			(9.2	)	23.7
Additions to property, plant and equipment	155.5			59.1		214.6
Total assets at year-end	$	2,304.7		382.5		$	2,687.2

Segment Information				Corporate and
(Millions of dollars)	Marketing			Other Assets		Consolidated
Year ended December 31, 2018
Segment income (loss)	$	214.2		(0.6	)	$	213.6
Revenues from external customers	14,362.3			0.6		14,362.9
Interest income	—			1.5		1.5
Interest expense	(0.1		)	(52.8	)	(52.9		)
Income tax expense (benefit)	69.5			(9.2	)	60.3
Significant noncash charges (credits)
Depreciation and amortization	124.5			9.5		134.0
Accretion of asset retirement obligations	2.0			—		2.0
Deferred and noncurrent income taxes (benefits)	39.0			(1.1	)	37.9
Additions to property, plant and equipment	169.2			24.6		193.8
Total assets at year-end	$	2,012.0		348.8		$	2,360.8

Segment Information				Corporate and
(Millions of dollars)	Marketing			Other Assets		Consolidated
Year ended December 31, 2017
Segment income (loss)	$	295.3		(50.0	)	$	245.3
Revenues from external customers	12,826.2			0.4		12,826.6
Interest income	—			1.3		1.3
Interest expense	(0.1		)	(46.6	)	(46.7		)
Income tax expense (benefit)	(2.9		)	(2.3	)	(5.2		)
Significant noncash charges (credits)
Depreciation and amortization	110.5			6.4		116.9
Accretion of asset retirement obligations	1.8			—		1.8
Deferred and noncurrent income taxes (benefits)	(61.3		)	10.9		(50.4		)
Additions to property, plant and equipment	234.0			39.7		273.7
Total assets at year-end	$	2,023.4		307.6		$	2,331.0